You can "optimise" out the stack frame in tail recursive code in perl5 using goto. E.g.:

sub fact {
    my($n, $a) = @_;
    return $a unless $n > 1;
    @_ = ($n-1, $n*$a);
    goto &fact;
}
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However, this is so wildly slow it's rarely worth the effort :-)

If perl6 doesn't manage to do tail-recursion optimisation I hope we at least get an efficient way to throw away a call-stack level so we can code it by hand.